To meet the recent demand for antimicrobial property in various fields, there have been proposed various antimicrobial agents (including antifungal agents and antimicrobial agents).
Among them, polylactic acids resulting from self-polycondensation of lactic acid hydrolyze easily and possess biodegradability and bioabsorbability, so are used as medical materials, e.g., operating thread. These polylactic acids possess a degree of polymerization high enough for themselves to have formability. Recently, however, studies have been made also about those having a relatively low degree of polymerization, i.e., lactic acid oligomers (see, for example, JP 10-139867A).
In JP 10-139867A, attention is paid not only to the antimicrobial property of lactic acid oligomers but also to sustained release and washing effect thereof. As to antimicrobial property, however, it is actually not always considered satisfactory.